[pdal] RE: Gist notes

[Mateusz Łoskot]

2011/12/9 Michael P. Gerlek <mpg at flaxen.com>:
> I should explain that my language allows for statements of the form
>
>        Field1 = Field2 + 10
>
> In Howard's case, the variable name "Field2" would be replaced by a GUID string.
> Without any annotation, the expression would then be ambiguous.

Even fstab file on Linux annotate UUID for drives.
However, with proper grammar, ambiguity drops to none and flexibility increases:

I've just given a quick stab at some PDAL expressions grammar using
Boost.Spirit:

https://github.com/mloskot/boost-spirit-workshop/blob/master/pdal_expressions.cpp

Certainly, it is not very useful at the moment as it only
parses/validates input.
But semantic evaluation can be added without problems (apart from the
Spirit learning curve).
See calc_utree.cpp example in the same repo.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net
Charter Member of OSGeo, http://osgeo.org
Member of ACCU, http://accu.org